Buggy code:
public class CastExpression extends Expression { public Expression expression ; public Expression type ; public TypeBinding expectedType ; public CastExpression ( Expression expression , Expression type ) { } public FlowInfo analyseCode ( BlockScope currentScope , FlowContext flowContext , FlowInfo flowInfo ) { } public static void checkNeedForEnclosingInstanceCast ( BlockScope scope , Expression enclosingInstance , TypeBinding enclosingInstanceType , TypeBinding memberType ) { } public static void checkNeedForArgumentCast ( BlockScope scope , int operator , int operatorSignature , Expression expression , int expressionTypeId ) { } public static void checkNeedForArgumentCasts ( BlockScope scope , Expression receiver , TypeBinding receiverType , MethodBinding binding , Expression [ ] arguments , TypeBinding [ ] argumentTypes , final InvocationSite invocationSite ) { } public static void checkNeedForArgumentCasts ( BlockScope scope , int operator , int operatorSignature , Expression left , int leftTypeId , boolean leftIsCast , Expression right , int rightTypeId , boolean rightIsCast ) { } private static void checkAlternateBinding ( BlockScope scope , Expression receiver , TypeBinding receiverType , MethodBinding binding , Expression [ ] arguments , TypeBinding [ ] originalArgumentTypes , TypeBinding [ ] alternateArgumentTypes , final InvocationSite invocationSite ) { } public boolean checkUnsafeCast ( Scope scope , TypeBinding castType , TypeBinding expressionType , TypeBinding match , boolean isNarrowing ) { if ( match == castType ) { if ( ( ! isNarrowing ) && ( castType == ( this . resolvedType . leafComponentType ( ) ) ) ) { tagAsUnnecessaryCast ( scope , castType ) ; } return true ; } if ( ( match != null ) && ( ( ( ( castType . isBoundParameterizedType ( ) ) || ( castType . isGenericType ( ) ) ) || ( expressionType . isBoundParameterizedType ( ) ) ) || ( expressionType . isGenericType ( ) ) ) ) { if ( match . isProvablyDistinctFrom ( ( isNarrowing ? expressionType : castType ) , 0 ) ) { return false ; } if ( isNarrowing ? ! ( expressionType . isEquivalentTo ( match ) ) : ! ( match . isEquivalentTo ( castType ) ) ) { this . bits |= UnsafeCastMask ; return true ; } if ( ( ( castType . tagBits ) & ( TagBits . HasDirectWildcard ) ) == 0 ) { if ( ( ( ! ( match . isParameterizedType ( ) ) ) && ( ! ( match . isGenericType ( ) ) ) ) || ( expressionType . isRawType ( ) ) ) { this . bits |= UnsafeCastMask ; return true ; } } } else <START_BUG> if ( isNarrowing && ( castType . isTypeVariable ( ) ) ) { <END_BUG> this . bits |= UnsafeCastMask ; return true ; } if ( ( ! isNarrowing ) && ( castType == ( this . resolvedType . leafComponentType ( ) ) ) ) { tagAsUnnecessaryCast ( scope , castType ) ; } return true ; } public void generateCode ( BlockScope currentScope , CodeStream codeStream , boolean valueRequired ) { } public Expression innermostCastedExpression ( ) { } public LocalVariableBinding localVariableBinding ( ) { } public int nullStatus ( FlowInfo flowInfo ) { } public StringBuffer printExpression ( int indent , StringBuffer output ) { } public TypeBinding resolveType ( BlockScope scope ) { } public void setExpectedType ( TypeBinding expectedType ) { } private boolean isIndirectlyUsed ( ) { } public void tagAsNeedCheckCast ( ) { } public void tagAsUnnecessaryCast ( Scope scope , TypeBinding castType ) { } public void traverse ( ASTVisitor visitor , BlockScope blockScope ) { } }

Fix:
if ( isNarrowing && ( castType . leafComponentType ( ) . isTypeVariable ( ) ) ) {